This program of research investigates the ability of mildly mentally retarded adults to perceive correctly certain classes of stimuli with distinctive attributes. These include global stereoscopic forms produced by random element stereograms and global motion defined forms produced by random element kinematograms, both of which impose substantial computational burdens on the visual system. The ability to integrate cues that define pictorial representations of three-dimensional space will also be examined, and the extent to which perceptual processing can be modified by perceptual learning will be explored. All stimulus conditions involve phenomena that emerge in infancy and are processed by automatic preattentive stages of the perceptual system. They are perceived effortlessly, without error, by nonretarded persons. Yet under these same conditions, mildly retarded persons exhibit substantial perceptual deficits. This is a surprising outcome in that mild retardation is generally regarded to be a product of intellectual and cognitive deficiencies. The proposed inquiry, which builds on prior work, seeks to specify more precisely the characteristics of these perceptual deficits. The resulting data should contribute directly to a deeper understanding of mental retardation. More generally they bear on the issue of the separability of cognitive and perceptual processes.